Solid sodium metal reacts violently with water, producing heat, hydrogen gas, and sodium hydroxide. How many molecules of of hydrogen are formed when 35 g of sodium are added to water?

Sodium reacts vigorously with water to form sodium hydroxide and hydrogen gas with production of heat.

2Na (s) + 2H2O (l) = 2NaOH (aq) + H2 (g)

The mass of sodium contains 35 g : 23 g = 1.522 moles.

Using the mole ratio of Sodium to hydrogen gas (1:2) we can get the moles of hydrogen produced, That is 1.522 moles : 2 = 0.761 moles

From the Avogadros law; one mole of a substance contains 6.02 * 10∧23 particles. Therefore, the number of molecules of hydrogen will be given by; 0.761 moles * 6.02 * 10∧23 = 4.581 * 10∧23 molecules

Therefure 4.581 * 10∧ 23 molecules are formed.